1. Field of the Invention
The present invention relates generally to a heat lamp assembly and in particular to an improved reflector for a quartz tube heat lamp assembly for drying printed materials.
2. Description of the Prior Art
Printing inks and coatings may be dried by a variety of methods which are well known in the prior art. Lower quality printing, for example newspapers and the like, is generally dried by exposure to the ambiant air and requires no supplemental drying because the paper tends to be highly absorbent. Furthermore, a certain amount of smearing and offsetting is considered acceptable in such lower quality printing. Higher quality printing, on the other hand, often requires supplemental drying because the inks and coatings tend to have relatively high moisture contents and the paper, being of a higher quality, is not nearly as absorbent as newsprint.
Drying can be supplemented by the use of anti-offset powder for absorbing the excess ink and coatings. However, the excess powder presents a maintenance problem and should not be used where it might interfere with the operation of the printing equipment.
Various types of heaters have also been employed for drying printed materials. For example, convection dryers have heretofore been employed for forcing heated air over the printed materials. Although convection drying is generally cleaner than using anti-offset powder, it tends to be relatively inefficient and may present environmental problems with disposing of the solvent-laden exhaust air. Furthermore, convection drying systems are often too large and expensive for relatively small printing presses.
Greater drying efficiency can often be achieved by using radiant heaters or heat lamps because the energy emitted thereby is largely absorbed in the liquid inks and coatings. Hence, relatively rapid evaporation can be achieved with minimal energy input by selecting heat lamps with output in the appropriate wave length range. For drying most printed materials, radiant energy in the short and medium wavelength infrared ranges (i.e. about 0.75 to 1.50 microns and 1.50 to 3.00 microns respectively) has been found to be particularly effective. Such energy is emitted by quartz tube heat lamps when they are heated to about 2400.degree. F. Such lamps are capable of raising the temperature of printed materials to approximately 95.degree. to 110.degree. F., which is the optimum range for evaporating the inks and liquid coatings thereon.
Typical quartz tube heat lamp assemblies include reflectors which partially surround the quartz tubes and tube housings which include the electrical connections. For example, such a quartz tube heat lamp assembly is shown in the Jacobi et al. U.S. Pat. No. 4,501,072, which is assigned to a common assignee with the present invention.
In spite of the aforementioned advantages of quartz tube, infrared drying systems, their application to certain types of printing equipment has been limited by problems encountered in transmitting infrared energy to the printed materials. In some printing presses, access to the printed materials is substantially blocked by the press structure. The infrared radiation from conventional quartz tube heat lamp enclosures covers only a portion of the printed materials; the rest being located beneath the press structure.
Heretofore there has not been a heat lamp assembly with the advantages and features of the present invention for mounting on a printing press of the type described herein.